From adb69a5a39bb58a0ac6866b64ede228692a80488 Mon Sep 17 00:00:00 2001
From: Matthew Hoops
Date: Wed, 24 Aug 2011 09:38:46 -0400
Subject: AUDIO: Rename Vag to XA

Vag is really an XA container, and one that we do not have a decoder for (nor need)
---
 audio/decoders/xa.cpp | 147 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 147 insertions(+)
 create mode 100644 audio/decoders/xa.cpp

(limited to 'audio/decoders/xa.cpp')

diff --git a/audio/decoders/xa.cpp b/audio/decoders/xa.cpp
new file mode 100644
index 0000000000..2b8c9b2d99
--- /dev/null
+++ b/audio/decoders/xa.cpp
@@ -0,0 +1,147 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "audio/decoders/xa.h"
+#include "audio/audiostream.h"
+#include "common/stream.h"
+
+namespace Audio {
+
+class XAStream : public Audio::RewindableAudioStream {
+public:
+	XAStream(Common::SeekableReadStream *stream, int rate);
+	~XAStream();
+
+	bool isStereo() const { return false; }
+	bool endOfData() const { return _stream->pos() == _stream->size(); }
+	int getRate() const { return _rate; }
+	int readBuffer(int16 *buffer, const int numSamples);
+
+	bool rewind();
+private:
+	Common::SeekableReadStream *_stream;
+
+	byte _predictor;
+	double _samples[28];
+	byte _samplesRemaining;
+	int _rate;
+	double _s1, _s2;
+};
+
+XAStream::XAStream(Common::SeekableReadStream *stream, int rate) : _stream(stream) {
+	_samplesRemaining = 0;
+	_predictor = 0;
+	_s1 = _s2 = 0.0;
+	_rate = rate;
+}
+
+
+XAStream::~XAStream() {
+	delete _stream;
+}
+
+static const double s_xaDataTable[5][2] =
+	{
+		{  0.0, 0.0 },
+		{  60.0 / 64.0,  0.0 },
+		{  115.0 / 64.0, -52.0 / 64.0 },
+		{  98.0 / 64.0, -55.0 / 64.0 },
+		{  122.0 / 64.0, -60.0 / 64.0 }
+	};
+
+int XAStream::readBuffer(int16 *buffer, const int numSamples) {
+	int32 samplesDecoded = 0;
+
+	if (_samplesRemaining) {
+		byte i = 0;
+
+		for (i = 28 - _samplesRemaining; i < 28 && samplesDecoded < numSamples; i++) {
+			_samples[i] = _samples[i] + _s1 * s_xaDataTable[_predictor][0] + _s2 * s_xaDataTable[_predictor][1];
+			_s2 = _s1;
+			_s1 = _samples[i];
+			int16 d = (int) (_samples[i] + 0.5);
+			buffer[samplesDecoded] = d;
+			samplesDecoded++;
+		}
+
+#if 0
+		assert(i == 28); // We're screwed if this fails :P
+#endif
+		// This might mean the file is corrupted, or that the stream has
+		// been closed.
+		if (i != 28) return 0;
+
+		_samplesRemaining = 0;
+	}
+
+	while (samplesDecoded < numSamples) {
+		byte i = 0;
+
+		_predictor = _stream->readByte();
+		byte shift = _predictor & 0xf;
+		_predictor >>= 4;
+
+		if (_stream->readByte() == 7)
+			return samplesDecoded;
+
+		for (i = 0; i < 28; i += 2) {
+			byte d = _stream->readByte();
+			int16 s = (d & 0xf) << 12;
+			if (s & 0x8000)
+				s |= 0xffff0000;
+			_samples[i] = (double)(s >> shift);
+			s = (d & 0xf0) << 8;
+			if (s & 0x8000)
+				s |= 0xffff0000;
+			_samples[i + 1] = (double)(s >> shift);
+		}
+
+		for (i = 0; i < 28 && samplesDecoded < numSamples; i++) {
+			_samples[i] = _samples[i] + _s1 * s_xaDataTable[_predictor][0] + _s2 * s_xaDataTable[_predictor][1];
+			_s2 = _s1;
+			_s1 = _samples[i];
+			int16 d = (int) (_samples[i] + 0.5);
+			buffer[samplesDecoded] = d;
+			samplesDecoded++;
+		}
+
+		if (i != 27)
+			_samplesRemaining = 28 - i;
+	}
+
+	return samplesDecoded;
+}
+
+bool XAStream::rewind() {
+	_stream->seek(0);
+	_samplesRemaining = 0;
+	_predictor = 0;
+	_s1 = _s2 = 0.0;
+
+	return true;
+}
+
+RewindableAudioStream *makeXAStream(Common::SeekableReadStream *stream, int rate) {
+	return new XAStream(stream, rate);
+}
+
+} // End of namespace Audio
-- 
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